Topotactic reductive fluorination of strontium cobalt oxide epitaxial thin films
Topotactic reductive fluorination of strontium cobalt oxide epitaxial thin films
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DOI：
10.1007/s10971-014-3499-x
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发表时间：
2015-08
影响因子：
2.5
通讯作者：
T. Katayama;A. Chikamatsu;Y. Hirose;T. Fukumura;T. Hasegawa
中科院分区：
文献类型：
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作者：
T. Katayama;A. Chikamatsu;Y. Hirose;T. Fukumura;T. Hasegawa
自从氧氟铜酸盐超导体被发现以来，人们一直在努力寻找新的过渡金属氧氟酸盐化合物。近年来，由于氧氟化物的低温合成，聚偏氟乙烯(PVDF)的拓扑定向氟化反应引起了人们的关注。在这项研究中，我们报道了用PVDF对SrCoO2.5前驱体薄膜进行点定向氟化制备SrCoOxFy外延薄膜。X-射线衍射分析表明，在150℃下氟化得到了具有阴离子空位的钙钛矿结构的SrCoOxFy膜，其面内晶格常数完全依赖于衬底。X射线能谱分析表明，氟化膜的化学成分为：SrCoO1.9±0.4F0.5±0.1；X射线光电子能谱分析表明，Co离子以2+和3+的混合价态存在。这一价态小于SrCoO2.5前驱体薄膜中的价态，表明PVDF对SrCoO2.5薄膜起到了还原氟化剂的作用。此外，在10℃时，SrCoO1.9±0.4F0.5±0.1薄膜也没有表现出铁磁性，表明Co离子之间存在反铁磁性相互作用。
Since the discovery of oxyfluoride cuprate superconductors, many efforts have been made to search for new transition-metal oxyfluoride compounds. Recently, the topotactic fluorination reaction using polyvinylidene fluoride (PVDF) has gained attention because of the low-temperature synthesis of oxyfluorides. In this study, we report the fabrication of SrCoOxFyepitaxial thin films via topotactic fluorination of SrCoO2.5precursor films with PVDF. X-ray diffraction analysis showed that the SrCoOxFyfilm, with an anion-vacant perovskite structure, was obtained by fluorination at 150 °C and that the in-plane lattice constant was completely dependent on the substrate. Energy dispersive X-ray spectrometry revealed that the chemical composition of the fluorinated film was SrCoO1.9±0.4F0.5±0.1and X-ray photoemission spectroscopy showed that the Co ions had a mixed valence state of 2+ and 3+. This valence state was smaller than that in the SrCoO2.5precursor film, indicating that PVDF acted as a reductive fluorinating agent for the SrCoO2.5film. Moreover, the SrCoO1.9±0.4F0.5±0.1film did not exhibit ferromagnetism even at 10 K, suggesting the presence of an antiferromagnetic interaction between the Co ions.